1. Field of the Invention
The invention relates to a vertical conveying apparatus for objects which are located one above the other in a stack, to a continuous furnace having such a vertical conveying apparatus, and to a carrier for such a vertical conveying apparatus.
2. Discussion of the Related Art
East German Patent Nos. 273,045 and 272,054 disclose apparatuses for vertical stacking of preferably shaped workpieces, in the case of which individual workpieces are arranged between two mutually opposite retaining beams and rest on retaining elements which are each provided for the individual workpieces. In the case of East German Patent No. 273,045, the retaining beams have circulating chains on the chain elements of which there are arranged the retaining elements in the form of projecting teeth. In the case of East German Patent No. 272,054, retaining catches for the workpieces are arranged in each case in the vertical direction on the retaining beams. In both cases, the individual workpieces are lifted from beneath into the position of the respective retaining elements by a lifting platform.
Likewise, West German Published Application No. 285,401 discloses a vertical conveying apparatus or a stacking apparatus which is intended for flat trays and includes a retaining device with four retaining elements which are arranged laterally in relation to the stack and can be brought into engagement with the lowermost tray and can be released therefrom again. The individual trays are advanced up to a position beneath the stack by a transverse conveying device. Each tray is advanced up to the stack from beneath by a lifting device, and the latter forces away the retaining elements of the retaining device, which is subject to spring force in the lateral direction, until the retaining elements spring back again beneath the advanced tray and thus retain the lifting device and the stack.
The disadvantage of these known vertical conveying apparatuses or stacking apparatuses resides in the fact that rubbing contacts, of the chain on the retaining beams, of the catches on the workpieces and of the retaining elements during disengagement and spring-back action, produce wear, with the result that stacking apparatuses of this type cannot be used in semiconductor technology.
West German Published Application No. 196 19 486 discloses a vertical conveying apparatus and a continuous furnace equipped therewith, in the case of which the problem of wear by rubbing contacts is avoided by a walking-beam concept. The disadvantages here are the mechanical complexity and the problem of the individual fan heaters being covered over by the retaining and/or transporting beams.
Taking West German Published Application No. 285,401 as the departure point, the object of the present invention is to provide a vertical conveying apparatus in the case of which wear is minimized.